USA Biology Olympiad (USABO) Practice Exam

In human biology, the loss of function of which gene is commonly associated with many cancers?

1. BRCA1

2. p53

3. RAS

4. MYC

The correct answer is: p53

The p53 gene is commonly associated with many cancers due to its critical role in regulating the cell cycle and maintaining genomic stability. It encodes a protein that acts as a tumor suppressor, meaning it helps prevent the formation of tumors by controlling the cell cycle, facilitating DNA repair, and triggering apoptosis (programmed cell death) in cells with damaged DNA. When the p53 gene is mutated or loses its function, cells can proliferate uncontrollably, accumulate further genetic mutations, and ultimately lead to the development of tumors. This loss of p53 function is a frequent occurrence in various types of cancers, making it one of the most well-studied and significant genes in the context of cancer biology. The other genes mentioned also play important roles in cancer, but their mechanisms are different; BRCA1 is primarily linked to breast and ovarian cancers through its role in DNA repair, RAS is an oncogene involved in cell signaling that can contribute to cancer when mutated, and MYC is a transcription factor that promotes cell growth and proliferation. While all these genes can be implicated in cancer development, p53's role as a guardian of the genome makes its loss particularly impactful across a wide range of cancer types.